The overall aim of this project is to identify the mechanism of mitochondrial assembly. Mitochondria are the main sources of ATP in eukaryotic cells, but they are also essential for many other biochemical processes. The specific aim of this project to isolate and characterize yeast mutants in which mitochondrial assembly is defective. Two such mutants (mas 1 and mas 2) have already been isolated using a "brute force" screen. Additional mutants will be sought by a variety of selection procedures. The genes affected in such mutants will be isolated by genetic complementation with genomic DNA banks from wild-type yeast. Availability of the genes should give information on the properties and the function of the proteins which participate in mitochondrial assembly.